Generally, a chip resistor is mainly constituted by an insulating substrate, a pair of front electrodes, a resistor body, an insulating protection layer, a pair of back electrodes, a pair of end-surface electrodes, etc. The insulating substrate is shaped like a cuboid. The pair of front electrodes are provided on lengthwise opposite edge portions of a front surface of the insulating substrate. The resistor body is provided between the two front electrodes. The insulating protection layer covers the resistor body. The pair of back electrodes are provided on lengthwise opposite edge portions of a back surface of the insulating substrate. Through the pair of end-surface electrodes, the front electrodes and the back electrodes are electrically conductively connected to each other respectively. Trimming is applied to the resistor body in order to adjust a resistance value thereof.
Recently, as the size and weight of an electronic device are reduced or the configuration of a circuit is complicated, there has arisen a case in which such a chip resistor is not only used in a surface-mounted manner on a circuit board but is also used as an inner layer type chip resistor embedded inside a resin layer of a laminate circuit board etc. In this case, a wiring pattern in a front surface of the resin layer is connected to the chip resistor inside the resin layer through via holes. Therefore, it is desirable that front surfaces of the end-surface electrodes connected to the via holes are wide and flat. A chip resistor configured to have wide and flat terminal electrodes in its front surface has been known as a configuration example satisfying such a demand (e.g. see Patent Literature 1).
In the configuration of the chip resistor disclosed in Patent Literature 1, the end-surface electrodes are extended from front electrodes to positions reaching an upper surface of a protection layer so that the end-surface electrodes whose front surfaces are made wide and flat can be formed. Each of the end-surface electrodes is formed to cover an overlapping portion (convex) between the corresponding front electrode and the resistor body. Therefore, there is a fear that the front surface of the end-surface electrode is not always flat but may be gently uneven.
To solve this problem, a chip resistor having the following configuration has been heretofore proposed, as described in Patent Literature 2. That is, a protection layer is formed to cover entire surfaces of front electrodes and a resistor body, and terminal electrodes are formed to extend around to a flattened upper surface of the protection layer so that front surfaces of the terminal electrodes can be flattened.
The chip resistor described in Patent Literature 2 is manufactured in the following manner. That is, a plurality of sets of front electrodes and resistor bodies corresponding to a larger number of chip resistors, and a protection layer covering entire surfaces of the front electrodes and the resistor bodies are formed sequentially on a large-sized substrate. An auxiliary protection layer made of wax etc. is formed on the protection layer. Then, first slits are formed in the large-sized substrate by dicing. End-surface terminals extending around from the insides of the first slits to an upper surface of the protection layer are formed. Then, secondary slits are formed in the large-sized substrate, and the auxiliary protection layer is cleaned and removed. Thus, single chips in each of which the end-surface electrodes are formed on the upper surface of the protection layer are manufactured.